Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2002-08-12
2004-11-23
Smith, Duane (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S764000, C210S205000, C210S258000, C210S259000
Reexamination Certificate
active
06821442
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates in general to a method for killing aquatic species and in particular to an environmentally friendly method for killing aquatic vertebrate and invertebrate invasive species.
The introduction of nonindigenous (exotic) species has had dramatic negative effects on marine, estuarine, and freshwater ecosystems in the United States and abroad (Elton, 1958; Mooney and Drake, 1986; Chesapeake Bay Commission, 1995) (Shortened literature citations are given throughout the specification. More complete citations are given at the end of the specification.). Effects include alteration of the structure and dynamics of the ecosystem involved, including extirpation of native species (OTA, 1993). The release of ballast water from ships is a major transport mechanism for nonindigenous aquatic organisms (Carlton, 1985) as recognized by the U.S. National Invasive Species Control Act of 1996 (P.L. 104-332).
Approximately 40,000 major cargo ships operating worldwide (Stewart, 1991) pump ballast water on board to ensure stability and balance. Large vessels can carry in excess of 200,000 m
3
of ballast which is released in varying amounts at or when approaching cargo loading ports. In 1991, U.S. waters alone received approximately 57,000,000 metric tons of ballast water from foreign ports (Carlton et al. 1994). Ship surveys have demonstrated that ballast water is in general a non-selective transfer mechanism—many taxa representing planktonic and nectonic organisms capable of passing through coarse ballast water intake screens are common. These include bacteria, larval fish and bloom forming dinoflagellates (Chu et al., 1997; Carton and Geller, 1993; Gail and Halsmann, 1997). The diversity of biota in ballast water is reflected in the examples of shipborne introductions of exotic species in the United States shown in Table 1 (NRC, 1996).
TABLE 1
Examples of Shipborne Introductions in the United States since the 1970s
Species
Origin
Location
Jellyfish (Hydromedusae)
Maeotias inexspectata
Black Sea
Chesapeake Bay
Black Sea Jellyfish
San Francisco Bay
Blackfordia virginica
Black Sea
Chesapeake Bay
Black Sea Jellyfish
San Francisco Bay
Water Fleas (Cladocera)
Bythotrephes cederstroemi
Europe
Northeastern North
Spiny water flea
America
Copepods (Copepoda)
Limnoithona sinensis
China
San Francisco Bay
Oithona davisae
Japan
San Francisco Bay
Sincalanus doerrii
China
San Francisco Bay
Pseudodiaptomus marinus
Japan
San Francisco Bay
Pseudodiaptomus inopinus
Asia
Columbia River
Pseudodiaptomus forbesi
China
San Francisco Bay
Crabs (Decapoda)
Hemigrapus sanguineus
Japan
Massachusetts to
Japanese short crab
Virginia
Mussels, Clams, and Snails
(Mollusca)
Dreissena polymorphia
Eurasia
Eastern North America
Zebra Mussel
Dreissena bugensis
Eurasia
Eastern North America
Quagga Mussel
Perna perna
South
Gulf of Mexico
South American Mussel
America
Potamocorbula amurensis
China, Japan
San Francisco Bay
Asian clam
Philine auriformis
New Zealand
California
New Zealand Seaslug
Moss Animals (Bryozoa)
Membranipora membranacea
Europe
Gulf of Maine to New
Kelp bryozoan
York
Fish (osteichthyes)
Neogobius melanostomus
Eurasia
Great Lakes
Round goby
Proterorhinus marmoratus
Eurasia
Great Lakes
Tubenose goby
Gynocephalus cernuus
Europe
Great Lakes
Ruffe
Mugiligobius parvus
Phillipines
Hawaii
Philippine Goby
Zebra mussel (
Dreissena polymorpha
) and Asian clam (
Corbicula fluminea
) introductions are of particular concern given their ability to (1) rapidly cover and change the physical structure of hard submerged substrates; (2) reduce open phytoplankton biomass and hence change desirable pelagic food webs; and (3) act as major macrofouling species of water intake structures used in municipal, agricultural, industrial, and power station water systems (Morton, 1987; Effler, 1994; O'Neill and MacNeill, 1991; Strayer, 1991; MassIsaac et al., 1991).
With regard to (3) above, the flow of water through the intakes carries with it a continuous source of food and oxygen for the organisms and carries away their wastes while the structures themselves protect the mussels from predation and environmental conditions such as wave activity and scouring by ice. Thus, the presence of the mussels and clams not only leads to reduced water pumping capacity but also can act as a seed source for downstream reaches of the water course involved. Control typically involves manual scraping and use of either thermal treatment or biocides (O'Neill, 1996). The biocides used include chlorine, quaternary and polyquatenary ammonium compounds or aromatic hydrocarbons (Waller et al., 1996).
Asian clams are found in 36 of the contiguous states of the United States as well as in Hawaii. Control of this species has been estimated in 1986 to cost the U.S. power industry over one billion dollars per year. The zebra mussel, introduced into the U.S. in 1986, has spread rapidly throughout the Great Lakes, St. Lawrence River, and waterways associated with the Mississippi River. It is expected that the mussels will, within 20-25 years, infest most areas south of Central Canada and north of the Florida Panhandle from the Pacific Coast to the Atlantic Coast. As the zebra mussel advances, the prognosis for native freshwater bivalve populations is bleak, especially for those populations of species considered threatened and endangered—zebra mussel densities of up to 400,000/m
2
have been reported and are thought to be the primary cause of the decline in unionids in the Great Lakes (MassIsaac et al., 1991).
A projected cost of two billion dollars has been proposed for zebra mussel control over the decade of the 1990's in the Great Lakes with this figure rising exponentially for North America as the mussels continue to expand their range. Expansion is also expected to dramatically increase the molluscicide load carried by our continental river systems. This is already a concern in the Mississippi River drainage and will no doubt lead to stricter future regulation of molluscicide usage at the local, state, and federal levels. Hence, there is a need for the development of alternative, environmentally neutral technologies to control exotic species already imported as well as to eliminate future ballast introductions of exotic species.
The National Research Council (1996) has identified some methods for shipboard treatment of ballast water. They are:
A. Filtration Systems
These systems cause the physical separation and removal of organisms above a certain size through use of deep media filters, coarse and fine strainers and continuously cleaned microscreens. In some cases, flow-through centrifugation systems are used to separate large particles prior to filtering to reduce filter clogging.
B. Biocides
Oxidizing biocides, such as chlorine, can be added to the ballast water by metering concentrated gas or solid chemicals or they can be generated electrically from sea water. Effective biocide concentrations are typically in the range of 1 to 5 mg/l. Non-oxidizing biocides can also be applied such as glutaraldehyde-based chemicals used in industrial water treatment.
C. Thermal Treatment
Inactivation of organisms in ballast water can be achieved by water heating directly through use of waste heat from ship propulsion systems. Ballast water would need to be heated to temperatures in the range of 35° C. to 45° C. and maintained there for a set period of time.
Additional options for treatment with possible limited applications include electric pulse and pulse-plasma processes, and ozonation. O'Neil (1996) reviews methods used to control zebra mussel colonization in water conduits including power plant cooling systems. They are:
D. Mechanical Controls
Scraping, “pigging”, high-pressure water jetting and abrasive blast cleaning is used to dislodge mussels and their bysal threads allowing for disposal. A prerequisite for mechanical removal is that the facility can withstand some level of infestation before the impacts of fouling to become too great.
E. Oxygen Deprivation (Hypoxia)
Zebra mussels can be killed by hermetically seal
Homer Mark
Pham Minh-Chau T.
Smith Duane
The United States of America as represented by the Secretary of
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